1. Field of the Invention
The present general inventive concept relates to an encapsulated colorant, a method of preparing the same and an ink composition including the encapsulated colorant, and more particularly, to an encapsulated colorant having at least two types of average particle diameters with different distributions, a method of preparing the same and an ink composition employing the encapsulated colorant.
2. Description of the Related Art
In general, in inkjet printers, colorants embody their inherent colors by selectively absorbing or reflecting visible light, and are classified as dyestuffs and pigments.
Dyestuffs are used in any material to be dyed, such as fibers, leathers, furs, and papers, thereby providing considerable fastness to washing in daylight hours, friction, etc. Pigments are coloring matters in the form of fine particles, and are directly adhered to a surface of the material to be dyed by physical means, to thereby provide their inherent colors.
Dyestuffs are dissolved in solvents such as water, however pigments are generally insoluble in the solvents, and therefore it is important to homogeneously disperse fine particle pigments in a solution and stably maintain the dispersed state without re-aggregation.
Although a water soluble dyestuff-type ink is superior in long-term storage stability since its homogeneity is maintained and also provides a clear color and brightness, it has poor water fastness, light resistance, etc.
On the other hand, although pigment-type ink has high optical density (OD), superior waterfastness and light resistance, and reduced bleeding between colors, it has poorer color clearness and long-term storage stability as compared to dyestuff-type ink. In addition, images printed using pigment-type inks have poor dry and wet rub fastness.
Furthermore, when printing in colors, such as in multicolor printing, with dyestuffs or pigments, bleeding between interfaces of each color occurs, and thus a clarity of the printed images is thereby reduced.
Thus, there is a need to develop an ink composition having superior storage stability which is an advantageous characteristic of the water soluble dyestuff-type ink, good water fastness which is an advantageous characteristic of the pigment-type ink, improved printed gloss, and improved rub resistance.
Meanwhile, a technique of adding a resin to an ink composition has been previously suggested in order to improve rub resistance of ink. However, the addition of the resin increases viscosity of the ink. Although a technique of adding resin particles to ink to inhibit viscosity of ink from being increased, rub resistance is not sufficiently improved since the resin particles and the pigments are independently dispersed in the ink.
In addition, when an ink composition including colorants with uniform particulate size is used, work efficiency may be reduced due to increased viscosity in low shear regions such as mixing and transferring the colorants and the colorants are aggregated in high shear regions such as inkjet ejection due to reduced stability of the particles, thereby blocking nozzles.
Since the above-mentioned problems are not sufficiently overcome merely by adding new additives to the ink composition, there is still a need to improve properties of ink compositions.